Space-time Engineering
Space-time Engineering
复制标题
时空工程
DOI：
10.1109/waina.2008.247
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
D. Pollack
中科院分区：
文献类型：
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作者：
T. Chruściel;D. Pollack
广义相对论提出了一种令人着迷的可能性，即通过创造连接遥远点的虫洞或连接不同宇宙的桥梁来变形空间。如果所讨论的点在空间中距离较远，虫洞提供了它们之间较短的路径。如果这些点在空间和时间上都很遥远，虫洞提供了一半的潜在时间机器。然而，爱因斯坦的理论对任何时候引力场的结构都有很强的限制（爱因斯坦“约束方程”）。这些方程将空间的几何形状与物质场的能量和动量联系起来，因此可以想象，试图创造虫洞总是会导致负能量密度，这在微观或宏观尺度上从未被观察到。在这里，我们展示了这种情况不会发生，并且在一般情况下，原则上可以创建连接空间中任意点的虫洞，同时保持能量正性的要求。事实上，如果我们想要连接的点附近没有物质，这甚至可以用真空虫洞来完成。第二个与此密切相关的问题是：物理学家能否根据邻近区域的几何知识，确定她所在的宇宙是否包含远离该区域的虫洞？由于爱因斯坦约束方程，虫洞或其他遥远的复杂拓扑结构的存在可能会反映在局部引力场中。这里我们也证明了这不是事实。更具体地说，我们表明，对于一般引力场构型（与约束一致），以及对于任何选择的点对，除了连接这对点的虫洞之外，还有其他相同的场构型。这同样适用于任意数量的虫洞，放置在任意位置
A fascinating possibility opened-up by general relativity is that of deforming space by creating wormholes connecting distant points, or bridges which connect distinct universes. If the points in question are distant in space, a wormhole provides a shorter path between them. If the points are distant both in space and time, a wormhole provides half of a potential time machine. However, Einstein’s theory places strong restrictions (the Einstein “constraint equations”) on the configuration of the gravitational field at any time. These equations tie the geometry of the space to energy and momentum of the matter fields, so that it is conceivable that attempts to create wormholes would always lead to negative energy densities, something which has never been observed on mezzoscopic or macroscopic scales. Here we show that this does not happen, and that in generic situations it is possible in principle to create wormholes connecting arbitrary points in space while maintaining the requirement of energy positivity. In fact, this can even be done using vacuum wormholes if there is no matter near the points that we wish to connect. A second, closely related question is the following: can a physicist determine, from the knowledge of the geometry of the nearby region, if the universe she lives in contains wormholes away from this region? Because of the Einstein constraint equations the presence of wormholes or other complicated topology far away could perhaps be reflected in the local gravitational field. Here we also prove that this is not the case. More specifically, we show that for generic gravitational field configurations (consistent with the constraints), and for any chosen pair of points, there are other field configurations which are identical except for a wormhole connecting that pair of points. The same holds true for an arbitrary number of wormholes, placed in arbitrary locations anywhere in